Self-biased control loops such as bandgap circuits and self-biased operational transconductance amplifiers (OTAs) can exhibit different operating points when powered up. For example, one operating point may occur where current flows (e.g. a normal desired operation), and another may occur where no current flows. To avoid the operating point where no current flows, a startup circuit may be required to inject current into the loop when powering up. Once the correct operating point has been reached, the startup circuit would be switched out to allow the normal behavior of the loop to take over. The switching in and out of the startup circuit is typically controlled using an analog closed loop circuit.
However, the use of an analog closed loop circuit for switching in and out the startup circuit introduces another loop (i.e. startup loop) into the circuit. When implementing such a circuit arrangement, effort must be taken to minimize the gain of this additional loop to prevent it rendering the circuit unstable. In startup loops where an inverter may be required, maintaining a stable circuit can become very challenging due to the high gain of the inverter.
Accordingly, there is a need for a circuit for controlling startup in an integrated circuit device that overcomes the deficiencies of conventional startup circuits in integrated circuit devices.